The Walther Model 4 was manufcatured between 1910 &
1928 and was their first successful Pistol

It was used by the Kaiser Wilhems Imperial Military Forces

The Model 4 is a relatively simple handgun of blowback
design, with a fixed barrel, an external extractor, and a concealed hammer.
Its most unusual feature is that (like its predecessor the Model 3) its
extractor and ejection port are on the left. The barrel acts as a guide
for the concentric recoil spring, which is held in place by a bayonette-type
lug that covers the front of the barrel, and by a sleeve at the rear which
also serves to cover the spring. When the slide moves rearward, it forces
the trigger bar down, disconnecting it from the sear. The safety is a
rotating thumb lever that positively locks the cocked hammer. Most safeties
have a checkered thumb-grip circle, but a few have circular grooves. There
is a screw on the backstrap of the grip that regulates the tension of
the flat hammer spring. The gun is slim and elegant, well-balanced, fitsthe
hand very nicely, and points instinctively.